1. Field of the Invention
This invention generally relates to exercise equipment. Specifically, this invention relates to dumbbells with adjustable weights.
2. Background Art
Dumbbells and barbells are commonly used for building body strength. These strength training devices may come in various configurations. For example, dumbbells can be categorized into fixed dumbbells and adjustable dumbbells. A fixed dumbbells has a pair of weights connected with a handle. Because each fixed dumbbell has a predetermined weights, one would need a set of different dumbbells in order to have different weights. Buying many fixed dumbbells would be expensive, and their storage would take more space. Therefore, adjustable dumbbells have become popular in recent years.
An adjustable dumbbell typically comprises a set of weights that allow a user to select the desired weights before use. Therefore, a single adjustable dumbbell may be sufficient for a user's need. The design of adjustable dumbbells can range from simple to elaborate. A simple design for an adjustable dumbbell may be accomplished by having individual disc-shaped weights with holes in the center to receive a handle. A user would select a plurality of the disc-shaped weights and then secure them to the handle by a locking mechanisms (e.g., a locking plate or nut).
More elaborate designs of adjustable dumbbells would include some selection mechanisms that allow a user to select the desired weights and lock the weights to the handle with ease. The selection mechanisms may be internal or external mechanisms (e.g., a rack-and-pinion mechanism), i.e., housed in the handles or external to the handles.
For example, U.S. Pat. No. 6,261,022, issued to Dalebout et al., discloses an external mechanism, in which a rotatable gripping member is attached to a cross member on the handle. The gripping member can be rotated to different angles to engage different sets of weights via cross bars that link paired weight plates.
Internal mechanisms are housed in the handles and typically involves a pair of sliding rods inside the handles. The sliding rods can be extended or retracted to engage different numbers of weight plates on both ends of the handles. The sliding mechanisms usually involve a rack-and-pinion or similar design.
For example, U.S. Pat. No. 7,090,625, issued to Chermack, discloses a design that contains a rack-and-pinion device within the handle, a transmission mechanism to move two extendable elements, a locking mechanism, and nested weight units that have bars attached to the sides of the plates for support.
While the prior art adjustable dumbbells provide convenient choices for the users, there remains a need for better design of adjustable dumbbells.